UDMA and bis-GMA matrix composite materials have been widely used as a dental restorative material for more than three decades. Clinical problems including poor wear resistance have led to development of a variety of differing composite constructions. Additionally, emphasis has been given toward the development of in vitro methods to predict clinical wear performance. The Alabama Dental Wear Simulator has been demonstrated to be a reasonable predictor of clinical performance. This device applies cyclic axial and tangential loading on the material surface via a high modulus stylus. However, little is known of the complex stress and strain distributions within the composite material when subjected to this loading environment and the resultin mechanisms of material loss. The purpose of my proposed research is to investigate the relationships of axial and rotational loading from the simulator to the specific microstructural and ultrastrucural mechanisms of composite material degradation under loading. Specifically, a series of bis-GMA composites with varying weight percent of both spherical or irregular particulate reinforcements will be investigated to determine the role of filler content from the monophase polymer. Correlations of observed wear to physical, chemical, and mechanical properties are anticipated. Analytical and finite element models will be constructed to contrast theoretical stress distribution to the laboratory data. The result of this study should new mechanistic understudying of the degradation of particulate polymer matrix composite structures under this loading profile and would be useful for future design optimization of the composite restorative materials.